Recent Advances in Ultra-wide Bandgap AlGaN and Ga2O3 Materials and Devices

Ultra-wide bandgap (UWBG) semiconductors such as high Al-content AlGaN and Gallium Oxide can provide significantly higher breakdown electric field than wide bandgap semiconductors such as GaN, and can provide excellent performance due to the higher breakdown electric field which leads to high Baliga Figure of Merit (for power switching) and high Johnson Figure of Merit (for high-frequency power amplification). This presentation will some areas where exciting progress on materials and device engineering is bringing us closer to high-performance III-Nitride (AlGaN) and Gallium Oxide electronics.<br/><br/>In the first part of this presentation, we will share recent results from work on lateral high-frequency AlGaN transistors. We will discuss simulations that show that better delay-breakdown combinations than possible in any material system today. We will then focus on two key experimental challenges associated with lateral UWBG AlGaN transistors – contact engineering, and extreme electric field management. We will show recent work from our team that uses advanced heterostructure engineered contacts to achieve state-of-art low contact resistance (&lt; 3.5 x 10^-7 Ohm-cm²) to ultra-wide bandgap AlGaN. We will also discuss approaches to exploit the high breakdown field (&gt; 8 MV/cm), applying high-permittivity BaTiO3 dielectrics to lateral transistors to prevent premature Schottky junction breakdown.<br/><br/>In the second part of the presentation, we will discuss our recent work on epitaxy, heterostructure design, and electrostatics to achieve high-performance -Ga₂O₃ lateral and vertical electronic devices and photodetectors. We will first discuss recent advances in materials growth and device design for lateral structures which enabled promising transistor demonstrations in the Gallium Oxide material system. Inserting an extreme-permittivity dielectric between the metal and semiconductor is an elegant way to prevent premature tunneling. Overlapping the gate with extreme-permittivity dielectric enabled Gallium Oxide transistors with excellent breakdown voltage (&gt; 600V) with a short gate-drain spacing of &lt; 1.1 , corresponding to a breakdown field &gt; 5.5 MV/cm. We will discuss our recent work on vertical Gallium Oxide electronics. -Ga₂O₃ trench Schottky barrier diodes fabricated through a Gallium atomic beam etching technique, with excellent field strength and power device figure of merit, were demonstrated. Reverse breakdown field strength of greater than 5.10 MV/cm is demonstrated at a breakdown voltage as of 1.45 kV.<br/><br/><br/>We acknowledge funding from Army Research Office DEVCOM UWBG RF Center (program manager Dr. Thomse Oder), Department of Energy/ National Nuclear Security Administration under Award No. DENA0003921, AFOSR GAME MURI (Award No. FA9550-18-1- 0479, project manager Dr. Ali Sayir), and Air Force Research Laboratory and Strategic Council for Higher Education under Agreement No. FA8650-19-2- 9300.